Protection circuit for high speed communication

Abstract

Provided is a protection circuit for high speed signal communication via a two-wire connection between the two output terminals of a PECL driver and the two input terminals of a PECL receiver. The PECL driver and receiver are supplied with power from individual power supplies. The protection circuit includes two diodes connected in series with a respective wire with their cathodes electrically coupled to the respective output terminal of the PECL driver and their anodes electrically coupled to the respective input terminal of the PECL receiver, and two resistors connected between the PECL receiver power supply and the anodes of the respective diode. The resistance of the resistors ensures forward biasing of the diodes when the receiver power supply is supplying power. A capacitor may be connected in parallel with the respective diodes.

What is claimed is: 
     
       1. A protection circuit comprising: a first diode, having a cathode and an anode, connected in series with a first wire, a first output terminal of a driver, and a first input terminal of a receiver;   a second diode, having a cathode and an anode, connected in series with a second wire, a second output terminal of the driver, and a second input terminal of the receiver;   a first resistor; and   a second resistor,   wherein said cathode of said first diode is electrically coupled to said first output terminal of the driver and said anode of said first diode is electrically coupled to said first input terminal of the receiver and to a first resistor,   wherein said cathode of said second diode is electrically coupled to said second output terminal of the driver and said anode of said second diode is electrically coupled to said second input terminal of the receiver and to a second resistor, and   wherein said first and second resistors are connected to a power supply in order to always forward bias the first and second diodes when the power supply is supplying power, such that said protection circuit blocks substantially all DC current flow from said driver to said receiver.   
     
     
       2. The circuit of claim 1, wherein the first and second wires comprise a transmission line. 
     
     
       3. The circuit of claim 1, wherein said first diode is connected between said first output terminal of the driver and said first wire and wherein said second diode is connected between said second output terminal of the driver and said second wire. 
     
     
       4. The circuit of claim 1, wherein said first diode is connected between said first output terminal of the receiver and said first wire and wherein said second diode is connected between said second output terminal of the receiver and said second wire. 
     
     
       5. The circuit of claim 1, wherein at least one of said first and second diodes are Schottky diodes. 
     
     
       6. The circuit of claim 1, wherein a first capacitor is connected in parallel with said first diode and a second capacitor is connected in parallel with said second diode. 
     
     
       7. The circuit of claim 1, wherein the driver is a PECL driver and the receiver is a PECL receiver. 
     
     
       8. A method for protecting a circuit comprising the steps of: supplying power to a first and second input terminals of the receiver, by a power supply;   connecting a first diode in series with a first wire, said first output terminal of the driver, and said first input terminal of the receiver;   connecting a second diode in series with a second wire, said second output terminal of the driver, and said second input terminal of the receiver;   electrically coupling a cathode of said first diode to said first output terminal of the driver;   electrically coupling an anode of said first diode to said first input terminal of the receiver and to a first resistor;   electrically coupling a cathode of said second diode to said second output terminal of the driver;   electrically coupling an anode of said second diode to said second input terminal of the receiver and to a second resistor; and   electrically coupling said first and second resistors to said power supply in order to always forward bias the first and second diodes when the power supply is supplying power, such that substantially all DC current flow from said driver to said receiver is blocked.   
     
     
       9. The method of claim 8, wherein the first and second wires comprise a transmission line. 
     
     
       10. The method of claim 8, wherein said first diode is connected between said first output terminal of the driver and said first wire and wherein said second diode is connected between said second output terminal and said second wire. 
     
     
       11. The method of claim 8, wherein said first diode is connected between said first output terminal of the receiver and said first wire and wherein said second diode is connected between said second output terminal and said second wire. 
     
     
       12. The method of claim 8, wherein at least one of said first and second diodes are Schottky diodes. 
     
     
       13. The method of claim 8 further comprising the step of connecting, in parallel, a first capacitor with said first diode and a second capacitor with said second diode. 
     
     
       14. The method of claim 8, wherein the driver is a PECL driver and the receiver is a PECL receiver.